Dynamo.



A. H. DARKER.

DYNAMO.

APPLICATION FILED 00110. 1911. 1 ,268,330. Patented June 4, 1918.

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FIGJ.

A. H. BARKER.

DYNAMO.

APPLICATION FILED OCT. I0, 191].

Patented June 4, 1918.

FIG-3.

A. H. DARKER.

' DYNAMOf APPLICATION FILED OCT. 10, I917.

1,268,330. Patented June 4,1918.

6 SHEETS- -SHEET 3- A. H. DARK-ER.

DYNAMO.

APPLICATION FILED 00110, 1917.

Patented June 4, 1918..

6 SHEETS-SHEET 4.

FIG. 13.

A. H. DARKER.

DYNAMO.

APPLICATION FILED ocT. us. 1917.

Patented June 4, 1918.

6 SHEETS-SHEET 5- F I G.l8.

FIGJZ A. H. DARKER.

DYNAMO.

APPUCATION FILED OCT. 0, 1911. 1 ,268 ,3 30. Patented June 4, 1918.-

6 SHEETS-SHEET 6- 28 29 FIG. /9.

W F/OEL Q A wrw mzw UNITED STATES PATENT o F CE.

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sp cm m m -rmn Patented June 4, 1918.

7 Application flled ootober 10, 191-7. 7 Serial N0. 195,094.

To all whom it may concern:

Be it known that I, ALFRED HENRY DAR- KER, a subject of the King ofGreat Britain and Ireland, residing at the Langham Hotel,

Portland Place, London, England, have invented certain new and usefulImprovements in Dynamos, of whichthe following is a specification.

This invention relates to brush and ter- 10 minal contact mechanism ofdynamo electric machines, especially such as are used for the lightingof railway and similar vehicles, and which are consequently drivensometimes in one direction and sometimes in the other.

one object of the present invention is to provide, in connection withthe brush rocker a contact mechanism comprising engaging parts capableof rocking one .in the other While maintaining eflicient electricalcontact in all positions of the parts. Such an arrangement permits ofeffectually employing the shifting of the brushes on the commutator,during reversal, for the maintenance of the constant polarity of thedynamo.

Another object of the invention is to provide rocking contact mechanismcapable of maintaining good and efficient engagement between the contactparts in all circumstances, and to provide self-cleaning contact 80parts, and, nevertheless to avoid offering appreciable or considerableresistance to turning, which is of importance when the said turning iseffected by the frictional engagement of the brushes with thecommutator.

A further object is the adaptation of brush and terminal contact of thekind referred to for the changing, interchanging or reversing of circuitconnections whenever the contact parts are rocked from one limitposition to the other. The principal advantage to be obtained inachieving this object is the utilizing of the mechanism in questionforthe changing overof batteries in double battery systems, whichchanging-over usually necessitates the provision of a separatelyenergized mechanism.

Yet another object is that of enabling brush and contact mechanismsuitable for use on a constant speed dynamo, such as a plain shunt woundmachine driven by a slipping belt, to be readily adapted, in a.

simple manner, for use on a variable speed self-regulating dynamo inwhich a subsidiary brush or brushes is or are employed.

A specific object, therefore, is to combine,

r with a rocker having the improved contact mechanism, asubsidiary'commutator brush gear, whereby the turning of the rocker,for.

reversal of the main brushes, carries the subsidiary brushes intoengagement with appropriate contacts. The contacts made 'in connectionwith the subsidiary brushes ma be those of the field winding of a variale speed dynamo.

The mvention, lastly has for its object to avoid the use of flexibleconnections between the brush holders and fixed terminals of the dynamoand to provide a simple arrangement possessing a longer life and greaterreliability than has been possible heretofore with exible connections.

The foregoing, together with such other objects as may hereinafterappear, or are incident to the present invention, are obtained by meansof constructions illustrated in preferred form in the accompanyingdrawings, wherein:

Figure 1 is a plan, partly in horizontal section of thecommutator end ofa four pole dynamo and showing the commutator, spindle bearing, brushrocker and a contact mechanism constructed in accordance with theseimprovements.

Fig. 2 1s a more or 1cm diagrammatic end elevation of the commutator endof the dynamo seen in 1, the four brushes of which are connecte in pairseach pair being connected with a contact arm of the improved contactmechanism.

Fig. 3 is a longitudinal sectional elevation of the commutator andcontact parts as modified for use with a two pole two brushv dynamo, thebrushes and contact parts being seen in this figure as when turned 90from either of the limit positions.

Fig. 4 is a more or less diagrammatic end view of Fig. 3 the parts beingshown in the limit position to which they are rocked when the dynamoruns in the direction of the arrow.

Fig. 5 is a view similar to Fig. 4 of a modification adapted for usewith a three brush dynamo, the subsidiary'brush holder being indicatedonly in dotted lines in order that two fixed contacts may both be seenclearly.

Fig. 6 is a longitudinal sectional elevation of a. fragment of thecommutator end of a dynamo showin particularly the contact devices forthe su sidiary brushes.

Fig. 7 is a diagram explanatory of the working of the arrangementillustrated in Fi s. 5 and 6.

Fig. 8 is a view similar to Fig. 3 of a further modification.

Fig. 9 is a diagram illustrating the dilierent connections made by anarrangement in which the contact devices, such as are seen in Fig. 8,are employed for changing over the circuit connections of the batteriesin a double battery installation when the movable parts are rockedthrough 180, as in the case of a two-brush two-pole dynamo.

Fig. 10 is a diagram illustrating a modification of the arrangement seenin Fig. 9.

Fig. 11 is a sectional view illustrating the addition of a third contactarm for use in a three brush dynamo of a known type.

Figs. 12 and 13 are diagrammatic views illustrating an adaptation of thecontact arrangements seen in Fig. 11 for producing the field circuitconnections in a three brush dynamo in opposite directions of running.

Figs. 14 and 15 illustrate further modifications of the arrangement seenin Figs. 11 to 13.

Fig. 16 is a sectional side elevation illustrating a furthermodification of the rocking contact devices or arms.

Fig. 17 is an end elevation and Fig. 18 is a side elevation of one ofthe contact devices seen in Fig. 16.

Fig. 19 is a diagram illustrating the operation of the parts seen inFigs. 16 to 18 and showing the parts in one extreme position.

Fig. 20 is a diagram similar to Fig. 19 but showing the connections madewhen reversal takes place and the contact arms are shifted through 180Fig. 21 is a diagram illustrating a switch arrangement applicable to theinstallation shown in Figs. 19 and 20.

Referring to Fig. l of the drawings, a is the armature, b are thebrushes, and 0 is the commutator. The four brushes are carried by theirrespective brush holders which may be of any suitable type and of whichno description need be given, as the present improvements are notconcerned with the particular type of holder employed. In Fig. 1, two ofthe brush holders are seen, namely 7) and b. I Fig. 2 the brush holdersare not seen but i the position to which they are rocked when the dynamoruns in the direction indicated by the arrow they would be opposite thepoints I) b b 12*. The four brush holders are mounted upon a rockercomprising a ring (Z which is carried by a ball bearing 6 on theexterior of the bearing sleeve f in which runs the end 9 otthe armaturespindle. One method of mounting the holders 6 to (2* consists inproviding each with an extension 71. which is bolted to an appropriateprojection (Z on the periphery of the ring (2, the extensions 71. beinginsulated by mica or suitable material 9'. Each extension It has an earor lug 7c and th? holders 6 b are connected as a pair by means of thecopper strip Z, Fig. 2, which is fastened by screws or studs to the earsor lugs on the extensions it of such holders 7) If. The extension k ofthe brush holder Z) is formed with an arm m which extends in the axialdirection beyond the end of the spindle and is then bent radially inwardtoward the axis, or is fitted with a radial arm. The end of the arm m,which may be suitably shaped as a disk at n, is received between, andgripped by, a pair of centrally situated spring blade contacts a,mounted upon a bracket 7), a bowed strip y connecting the bracket with aterminal 1" of the dynamo. The bracket 7) is secured upon a terminalboard 8, of suitable insulating material, suitably mounted at the outerend of the bearing sleeve Outside of the extension h of the brush holder6 is secured a plate t, which is insulated from the said extension byinsulation j, as seen clearly in Fig. 1, and this plate t is connectedby means of copper strips u, Fig. 2, with the ears or lugs 70appertaining to the brush holders 6 b, so that these latter areconnected as a pair. The plate t is formed with an arm m similar to thearm m aforesaid, and the end a of the arm m is received and grippedbetween spring contacts 0 arranged behind the contacts 0 aforesaid andwithin the bow of the strip 9. The

contacts 0 are mounted on one end of a strip 9 which connects thecontacts 0 with the other terminal r of the dynamo.

It will be seen therefore that the ends n n of the arms on m are capableof turning in the contacts 0 0, after the manner of pivotal connectionshaving the axes of the pivots coinciding with the axis of the armaturespindle. As the arms m m have only to rock through an angle of about 90,when the direction of runnings is reversed, this amplitude of movementis possible without the arms m m encountering any obstruction. The ringcl is rocked in one direction or the other, according to the directionof running, by reason of the frictional engagement of the brushes 6 withthe commutator 0, or if desired, by means of electrical or mechanicalclutch parts, and suitable stops are provided, as usual, for limitingthe rocking motion in either direction so to properly position thebrushes 6. As the frictional engagement between the ends n n of the armsm m and the contacts 0 0 occurs between such small areas situated at thecenter of revolution,

relatively little resistance is offered to the turning movement producedby the engagement of the brushes 6 with the commutator, the diameter ofwhich latter is relatively large compared with the diameters of the endsa n, or by the engagement of suitable are in constant gripping ent withthe contacts o the circuit is never broken,

and the contact surfaces are practically never exposed to any extent,and are self cleaning.

In the modification illustrated in Figs. 3

and 4, there are only two brush holders 5' Y b 180 apart, the dynamobeing a two pole machine in which the brushes b must be capable ofrocking through about 180 u n reversal of the direction of e brushholders are not seen in Fig. 4 ut the positions, for the direction ofindicated by the arrow, are 0 posite the reference characters 6' b. Therush holders are mounted by means of extensions it upon the rocker ring(1, and in the case of the holder b the extension h is formed with abent ,con-

tact arm m the end n of which is received and gripped by the centrallysituated spring contacts 0'. Now if, upon reversal, the holder 12 isrocked throu b about 180 in the direction opposite to t hat indicated bythe arrow Fig. 4, so as to exchange positions with the holder b, it will.be clear that the extension h of theholder 6 cannot be fitted with acontact arm, as in the case of the holder 12*, because such arm wouldencounter the supporting bracket f of the bearing sleeve f. Therefore acontact arm m is mounted. outside of, but-insulated from, the arm m, andis electricall connected with the extension h of the ho der 1) by meansof the copper strip v. The end n of the arm m is received and gripped bythe centrally situated spring contact 0. The contacts 0 o' are mountedupon a suitable terminal board 8 and connected with appropriate dynamoterminals r 1" in any convenient manner. The arrangement above describedpermits the free unobstructed movement of the arms m 121/ throughabout180 in the direction aforesaid, upon the direction of running beingreversed. A suitable means of arresting the ring (1 in either ofthelimit positions consist of small bolts w screwed into a projection onthe ring and adapted to strike against either the projection a; or 3 onthe framing according to the direction of running.

In the case of a three brush dynamo, in which there are two main brushesand one subsidiary brush, a third arm similar to the arms m mf and athird contact similar to 'the contacts 0 0 may be added and suitable thecenter than the contact 6.

brush holder orholders'may bemounted upon a separate rocker and thecontact arms appertaining to the subsidiary brush or brushes would becarried b this second rocker, as will be readil un erstood.

In the case of a subsidiary brush dynamo, however, the third arm may bedispensed with, as seen in Figs. 5 to 7, which illustrate an arrangementsimilar to that in Figs. 3 and 4, but with subsidiary brushes in holders6 6' supported upon the ring d by means of extension pieces which arebolted to, but insulated from, the ring d, as seen in Fig. 6.. Only oneof the subsidiary brushes is in action at one and the same time andthese brushes are supported upon the ring d in such'positions thatwhenelther of them is in action, according to the direction of running,it is correctly placed in relation .with .the main brushes. The brushholder 6 has a projecting contact?) adapted for engaging with a fixed,fork contact'b" in the direction of running indicated by the arrow inFig. 5. The brush holder 6 is provided with a similar projectin contact6 adapted for engaging a fixed ork contact b which is situated a littlefarther from Therefore when the brushes rock through 180 from theposition seen in Figs. 5 and 7 in the reverse direction to thatindicated'by the arrow, the projection b passes out of engagement withthe contact b and then beneath the contact 6 and finally the projectingcontact I) on the holder b" comes into engagement with thefixed contactb. As will be seen from Fig. 7, one terminal of the field winding 10ofthe dynamo is connected to', say, the negative main of theinstallation which is connected with the contact 0. The latter is incontact with the disk n on the end of the armxm. which is connected bythe strip conductor -v with the negative brush holder 6'. The otherterminal of the field winding '10 is connected to the two fixed contacts5.

winding '10 is connected between the neg'ative brush holder b and thesubsidiary brush holder 6 in advance in the direction of revolution. Thedynamo poles indicated in Fig. .7 are shifted around through 90 ascompared with Fig. 5 so as to give the con-- ventional disposition ofthe main brush be tween the poles. In the reverse direction of rotationthe negative brush holder 6 will be brought around to the position inwhich the brush holder 1) is seen and the subsidiary brush holder 6'will engage by its projecting contact 6 with the fixed contact 6, sothat, in this reverse direction of running, the field winding. 10 willstill be connected between I the negative brush holder and a subsidiarybrush holder in advance thereof. This arrangement enables a position tobe determined for the intermediate brush which gives a wider or lessspan than 90 on the commutator as may be desired, so that a very fineadjustment and varied output curve can be obtained. With thisarrangement, the subsidiary'brush which i in action in one direction ofrunning may have the same angle of advance as the subsidiary brush whichis active in the opposite direction of running, or it may have a.diderent angle of advance according to whether or not the conditions arethe same in the two directions of running. The subsidiary brush. whichfor the time being is idle. is very close to the neutral line, so thatit does not have any adverse influence such as it would have if it werein a position to short circuit active conductors. For a four pole dynamoa similar arrangement could be readily devised possessing similaradvantages. It will thus be seen that only very simple modifications arerequired for changing a shunt wound dynamo, suitable for being driven bya slipping belt, into a self-regulating dynamo which may be driven so asto partake of all the speed variations of the driving axle.

When an installation comprises two batteries, as in Figs. 9 and 10, itis necessary, for well-known reasons, to interchange, from time to time,the connections of the batteries w and y, and this may be accomplishedby means of an adaptation of the improved mechanism hereinbeforedescribed. For example, and as illustrated in Figs. 8 and 9, the contactend of the arm m, which is assumed to be in connection with the positivebrush of the dynamo, is adapted for engaging with a number of contactsas hereinafter explained. The end a of the arm m, which is connectedwith the negative brush, need only engage with a single contact 0 asbefore. The disk end a of the arm m, is oiiset from the said arm m andis composed of two portions n and a separated by insulation a theportion at being integral with the arm m and the portion n beingcompletely insulated. In the portion n there is an inset of insulationn, Fig. 9, or, of course, a suitable gap may be out in the portion n.Around this disk-shaped end of the arm m are four fixed contacts 1, 2, 3and 4: which constantly engage with the disk after the manner of thecontacts 0 and 0 above de scribed. The contact 1 is connected with thepositive lead to the battery y; the contact 2 is connectedwith thecontact 4 by a conductor 9; the contact 3 is connected with the positiveto the battery m and the contact 4 is connected with the lightingcircuit 2. The usual lamp resistance '0' is connected between thepositive terminals of the batteries a: and 3 and any suitable means areprovided forshort circuiting this resistance at w when the dynamo speedfalls below a predetermined minimum, in the well-known manner. Anclectro-magnetio main circuit closer is shown at 5 and needs no furtherdescription as it may be of any well-known kind and may be adapted forclosing the short circuit at w when it opens the main circuit, also inthe well-known manner.

When the direction of revolution is that indicated by the arrow, thearms m m occupy the positions seen in full lines, in Fig. 9, this figurebeing diagrammatic and showing the arm m removed from behind the arm m.In this position of the parts. current from the positive brush passesthrough the arm m to the disk portion 71 and into contact 1. The contact2 is on the insulation a and makes no circuit. Consequently, the saidcurrent passes from contact 1 through the conductor 6, a part going intothe battery 3 to charge the latter. and a part flowing through theresistance 1*. conductor 7, Contact 3, disk portion n, contact 4 andconductor 8 to the lamps. Under these conditions, the battery :0 may attimes receive a slight charge and at other times may slightly dischargeto assist the dynamo in supplying the lamps, and a'battery so connectedis said to be floating. lVhen the direction of revolution is reversed,so that the arms m m are turned through 180 to the dotted position, thedisks on the ends of the arms turning in respective contacts, the

.disk portion 41. engages the contact 3 so that the battery as isdirectly supplied with charging current. The insulation 12 is oppositethe contact 4 so that the latter makes no circuit. The disk portion aconnects the contacts 1 and 2, so that some current from the conductor 7passes through the resistance '22 to the conductor 6, through contact 1,disk portion n, contact 2, conductor 9, contact 4, and conductor 8 tothe lamps. The battery y is now floating, and it will be seen,therefore, that the reversal of the rocking parts eflects a change-overof the battery connections in the desired manner.

In the modification illustrated in Fig. 10

' which is particularly adapted for a four pole dynamo, the disk part non the arm m when the direction of revolution is that indicated by thearrow, is in position for ma king connection between the arm m and thefixed contacts 3 and 4. This means that current from thepositive brushof the dynamo, passing through the arm m and arriving at the disk part17/ divides into two parts, one part passing through the fixed contact 3to the battery a: and the other part passing through the contact l.resistance 1) and conductor 8 to the lamps. At times a little of thecurrent in the conductor 8 will flow through the contact 2, disk portiona and contact 1 to the floating battery y, while at other times a littlecurrent will flow reversely from the battery 3 to assist in supplyingthe lamps. In the reverse direction mouse of running the arms m m turnthrough 90 only to the vertical positions indicated by the verticaldotted lines in Fig. 10. In this 'tion, the disk portion 10' will touchthe ed contacts 4 and 1, so that the battery y will then be directlycharged and the lamps will receive current through the resistance 1).The disk portion n being then in contact with 3and 2, the battery a:will be floating and may take in or give out a little current by way ofconductor 8, contact 2, disk portion n, and contact 3. In Fig. 10 whenvthe main circuit closing switch 5 opens, it closes a subsidiary switchat w and connects a small resistance v in parallel with the resistance'0.

Fig. 11 shows an arrangement in which a third arm m is mounted upon therocker and is connected with a subsidiary brush in the same manner asthe arms m m are connected with the main brush holders as abovedescribed. Now in some self-regulating dynamos, a main field winding 10,Fig. 12, is connected, in the direction of running indicated b the arrowbetween the positive brush an the subsidiary brush in advance of thepositive brush, but, upon reversing the direction of running, thebrushes take up the position seen in Fi 13, and in order that the sameeffect may e obtained as in the direction of running in Fig. 12, thewinding '10 must be connected between the negative brush and thesubsldlary brush, because the latter is now in advance of the negativebrush havi regard to the direction of revolution indicated by the arrow.

In order to accomplish this, one terminal of the winding 10 is connectedto a fixed contact 11 which is engaged by the arm m, in one extremeposition of the arms, as seen in Fig. 12, and the opposite terminal ofthe field winding 10 is connected to a fixed contact 14 which is engagedby the arm min' the other extreme position of the arms, as seen in Fig.13. Contacts 12 and 13 are arranged to grip a disk on the end of the armm, which disk is offset as in the case of the disk on the arm m in Figs.8 and 9. One portion of the disk is of-insulation, as indicated by theshaded area 15, and the other portion a may be integral with the arm mso that in either of the extreme positions of the arms, the arm 'm is inelectrical contact with either the contact 12, or

the contact 13, according to the direction of revolution. That terminalof the winding 10 which is connected to the contact 11 is also connectedto the contact 12, and the opposite terminal is connected to the contact13. In the direction of running indicated in Fig. 12, the arm m is inengagement with the fixed contact 11, and the contact 13 is on the metalportion n of the disk on the arm m so that the windin 10 is connectedbetween the positive and s sidiary brushes,

the contact 12 being on the insulation of the said disk. In the oppositedirection of running indicated in Fig. 13, the parts having turnedthrough 180, the arm m is in engagement with the contact 14, contact 13is on the insulation 15 and the contact 12 is now engaging the metalpart n of the disk so that thewinding 10 is connected up between thenegative and subsidiary brushes. Therefore, in either direction ofrunning the flow of current through the fieldwinding 10 will be in thesame direction, as is in mated by the arrow placed near to the windin10.

In t e modification seen in Fi 14, a disk n on the end of the arm 'm. iseccentric to the axis of the armature spindle indicated by Therefore. inthe extreme position "shown in full lines the disk n will engage thecontact 12 and in the opposite varms being indicated by the full anddotted lines as before.

In the modification seen in Figs. 16 to 18, the contact disk n on thearm m engages a fixed contact 0 as before, but it is also fitted withoff-set disk parts 16 and 17 the part 16 being connected by screws tothe disk n so as to be in electrical connection therewith, and the part17 being connected by screws 'but hav ng insulation 18 interposed, sothat the part 17 is completely isolated from the disk n and arm m. Thepart 17, moreover, is insulated from the part 16 by an air gap 19, or bya layer of insulation, and is lar r than the part 16, the peripheral arcof t e latter being a little more than 90 and the eripheral arc of thepart 17 being consideralbly more than 180. The disk parts 16,17 are inoperative engagement with three fixed contacts 20, 21, and 22, connectedrespectively to terminals 23, 24 and 25'on the terminal board, the

terminal r as m will now be described. The disk 'n' on the arm m isshown, in Figs. 19 and 20, as of larger diameter than the disk composedof the parts 16 and 17, simply for conven he contacts 11 and 14 aredirectly to the battery as.

icncc in making up the diagram. Current passes from the disk a into thecontact 0' and from the latter through the conductor :26 to the lowerterminal of the lamp resistance v, the conductor being continued to afan motor circuit 27 if the installation comprises such motors inaddition to lamps; Instead of, or in addition to, fans, electric heatersand other apparatus may be employed. The upper terminal of theresistance v is connected not only to the lamps a" through the lampsswitch, but also by conductor 28 with the terminal 21 of the contact 21,so that the current also passes through :28, 2t and 21 to the insulateddisk part 17 and through the latter to the contact 22, terminal 25, andconductor 29 to the battery w. Current from the disk 11/ also passesinto the disk part 16, through contact 20, terminal 23 and conductor 30to the battery 3 Thus the battery y is directly charged by the dynamocurrent, whereas the battery as is floating.

In the reverse or clockwise direction of running indicated in Fig. 20,the arms at m and their contact disks have turned through 180. and itwill be seen that the terminal-contact 22 of the battery 00 is now inengagement with the disk part 16 so that charging current from thedynamo can pass The insulated disk part 17 now electrically connects thecontacts 20 and 21, so that current from the disk 91. passes through thecontact 0' terminal 9* conductor 26, and resistance r to the lamps .2and also from the upper terminal of the resistance '0 through conductor28, terminal 24, contact 21, disk part 17, contact 20, terminal 23 andconductor 30 to the battery t. In this direction of running therefore,the battery ;2 is the floating battery. It will be observed that as thefan motor. current is taken directly from the contact 0 in eitherdirection of running the potential applied to the fan motors is alwaysthat of the positive brush of the dynamo. The main circuit closer 5 isadapted, when opening the main circuit, to connect a resistance '0 inparallel with the resistance o. The main lamp switch 31 has anadditional contact 32 connected with the upper terminal the resistancesc o and an additional contact 33 connected with the conductor 26. In theoff position of this lamp switch, the brush, or other switch device,connects the contacts 32 and 33 and thus short circuits the resistances.

According to Fig. 21, the core of the solenoid of the main circuitcloser 5 is adapted to operate a double switch brush 34. This brush hasits hinge end connected with the upper terminals of the resistances 'v'v and when the core. of the solenoid falls to open the main circuit thebrush 34 makes contact with two terminals. 35, 36. These terminals arerespectively connectedto points 35 and 36 Fig. 20, in theconductors 29and 30 respectively. Therefore, when the main circuit is opened at 5,the switch 34 makes connection between the conductors 29 and 30 and theupper terminal of the resistances o 42 so that the batteries may thensup ly the lamps direct, no current having t en to pass through thecontact disk part 17. In order that the dynamo may be excited with fullbrush voltage, the field windings may be connected between the terminals1" and r. Also the connections for the potential coil of the maincircuit closing solenoid may be taken from these terminals.

I claim 1. Rocking terminal contact mechanism for dynamo electricmachines comprising a rocking member, contact members mounted on saidrocking member and extending toward the center of revolution, andfixedly mounted contacts adapted to engage the inner end of said contactmembers in such manner as to permit of the desired rocking movementthereof.

2. Rocking terminal contact mechanism for dynamos comprising a rocker,contact arms mounted on said rocker and extending toward the center ofrevolution, and fixedly and centrally mounted contacts adapted to engagethe inner ends of said arms and permit of the desired rocking movementthereof.

3. Reversing brush gear for dynamo electric machines comprising arocking support for commutator brush holders, conductor arms mounted onsaid support and connected with respective holders said arms having freeends extending toward the center of revolution, and fixedly mountedcontacts adapted for engaging the inner ends of said arms and permittingof the desired amplitude of rocking motion thereof.

4:. Reversing brush gear for dynamo electric machines comprising arocking support for commutator brush holders, arms extending fromrespective holders toward the center of revolution, and fixedly mountedcontacts in engagement with the inner ends of said arms at said center.

5. Reversing brush gear for dynamo electric machines comprising arocking ring support, commutator brush holders, mounted around saidring, conductor arms extending from said holders away from thecommutator and toward the center of revolution, and central fixedcontacts adapted for engaging the inner ends of said arms whilepermitting the rocking movement thereof.-

6. Reversing brush gear for dynamo electric machlnes comprising arocking brush holder support, conductor arms connected with respectiveholders and extending to the center of revolution, said arms beingarranged so that their free ends are one behind the other in the line ofthe axis of said spindle, and fixedly supported central contactsarranged one behind the other along said line and engaging with theinner ends of appropriate arms in such manner as to permit rockingmovement thereof around said axis.

7. In a dynamo electric machine and in combination a rocking brushholder support, conductor arms extending from some of the brush holderson said support toward the center of revolution, fixed central contactsappropriately arranged for engaging the inner ends of respective arms,while permitting rocking motion of the latter projecting contacts onother brush holders, and fixedly mounted contacts adapted for engagingsaid projecting contacts in the limit positions of said rocking support.

8. In a dynamo electric machine and in combination a rocking brushholder support, conductor arms connected with respective holders andextending toward the center of revolution, disk shaped contact pieces onthe ends of said arms, and fixedly supported central contacts engagingwith;

respective disks in such manner as to permit rocking movement thereofaround said axis.

9. Brush reversing and switching gear for dynamo electric machinescomprising a rocking support, brush holders thereon, an arm extendingfrom one of said holders and toward the center of revolution, a switchcontact disk on the inner end of said arm, and a plurality of fixedcontacts around the periphery of, and adapted to engage with, disk, thepartial revolution of said said disk in relation to said contacts beingadapted for performing switching operations.

10. Brush reversing and switching gear for dynamo electric machinescomprising a rocking support, brush holders thereon, an arm extendingfrom one of said holders and toward the center of revolution, a disk onthe inner end of said arm said disk being partly of metal in electricalconnection with said arm and partly of insulation, and a plurality offixed contacts around said disk adapted to engage therewith, the partialrevolution of said disk in relation to said contacts being adapted formaking difierent circuit connections in one limit position from thosewhich are made in the other limit position or" the rocking support.

11. Brush reversing and switching gear for dynamo electric machinescomprising a rocking support, brush holders thereon, an arm extendingfrom one of said holders and toward the center of reyoluti'on, an offsetdisk on the inner end of said arm said offset disk being composed of twoportions one of which is connected with and the other insulated fromsaid arm, and a plurality of fixed contacts around each disk adapted toengage therewith.

12. Brush reversing and switching gear for dynamo electric machinescomprising a rocking support, brush holders thereon, an arm extendingfrom one of said holders and toward the center of revolution, said armbeing formed at its inner end with a flattened disk portion, an off-setcontact disk in twoparts secured concentrically to said disk portion oneof said parts being completely insulated, a fixed contact engaging thedisk portion of contacts around the periphery o the two part disksubstantially as set forth.

ALFRED HENRY BARKER.

of the arm, and a lurality

